The invention more particularly concerns a unidirectional flow limiter of the type described and illustrated in German Patent Specification No DE-A-3 215 696. German Patent Specification No DE-A-3 215 696 discloses a unidirectional flow limiter comprising a tubular body, each of the two oppositely disposed axial ends of which is provided with means for connection to a fluid conduit system, comprising an axial duct passing through a valve seat and in which is accommodated a ball for closing off said duct, being movable between the seat and an abutment element which is axially spaced from the seat. In by-pass relationship to the first duct at the boundaries of the valve, a second duct is defined by two radial orifices which are disposed in the wall of the body on each side of the seat, and by an annular conduit connecting them to the exterior of the body, the conduit being disposed between the latter and an external sleeve. A separate ring which is mounted rotatably on the body makes it possible to uncover to a greater or lesser degree the mouth of one of the radial orifices where it opens into the annular conduit, so that by rotary movement it is possible to adjust the flow section of the by-pass duct and therefore the flow which can pass therethrough.
The throttle ring is advantageously made of elastic material and is mounted with a slight radial gripping effect on the cylindrical surface portion which receives it.
It appeared desirable to improve certain aspects of a flow limiter of that type in order to improve the performance thereof and to reduce the manufacturing costs thereof.
In fact, in the limiter disclosed in that document, the body is a solid metal component with the valve seat machined directly in the internal bore therein. Such cutting operations are generally expensive. In addition, the axial abutment element for the closure ball is a separate added component which is produced either in the form of a transverse pin engaged into an opening in the wall of the tubular body, or in the form of an axial finger which extends from the end face of a liner member which is a force fit in the internal bore in the body.
Besides the cost of all those machining and assembly operations, the operation of fitting the retaining element into position gives rise to stresses in the body which can result in deformation phenomena, in particular at the bearing surface of the throttle ring, so that there is no guarantee that the ring will enjoy good contact and sealing integrity at that location is less than perfect, which would be detrimental to good operation of the flow limiter if the body were not metal. Now, making such a device entirely of plastics material is a highly important factor in terms of reducing cost, but in that case the known structure is not appropriate. It is an object of the present invention to resolve this problem.